The invention relates to refrigeration systems in general, and more particularly to evaporators in which cooling is produced by evaporation of a liquid refrigerant. Still more particularly, the invention relates to improvements in methods of and in apparatus for checking the icing of evaporators in refrigeration systems.
The deposition of frost and ice on evaporators of refrigeration systems is a well known and highly undesirable phenomenon. The surface of the evaporator collects moisture from the flow of air which is admitted into or is forced to enter the inlet or inlets of the evaporator so that the inlet or inlets are covered with ice and/or frost within hours. This necessitates a defrosting, a procedure which normally involves an interruption of operation of the refrigeration system. Numerous proposals were made to delay the icing and frosting of the evaporator and to thus prolong the intervals of operation of the refrigeration system. Deicing or defrosting is desirable on the additional ground that the output of the evaporator and the efficiency of the refrigeration system decrease with progressing icing of the inlet or inlets of the evaporator.
One presently known proposal is disclosed in German Pat. No. 117,943 according to which the flow of air which is to enter the evaporator is caused to pass through hygroscopic salts. Such proposal is not satisfactory in modern refrigeration plants wherein large quantities of hygroscopic material would have to be kept close to the evaporator in order to prevent or delay the icing.
German Offenlegungsschrift No. 1,551,332 proposes to employ an evaporator which is provided with external ribs or fins and to place an array of smooth-surfaced pipes in front of the evaporator. Moisture is supposed to deposit on the surfaces of the pipes. The pipes delay the icing of the evaporator and exhibit the advantage that ice can be more readily removed from their smooth surfaces than from the ribbed or finned surface or surfaces of the evaporator. However, the effectiveness of the array of pipes is not entirely satisfactory and, though it is simpler and easier to remove ice and frost from smooth-surfaced pipes, such operation is far from being simple and invariably takes up a rather long interval of time during which the refrigeration system remains idle.
European Pat. No. 0 089 991 proposes to place a blower in front of the inlet of an evaporator and to install a filter between the blower and the inlet so that the filter gathers moisture and thus delays the icing of the evaporator. This proposal exhibits the drawback of the proposal which is disclosed in the German Offenlegungsschrift. All of the above-enumerated prior proposals share the drawback that they can merely delay the icing and only for relatively short intervals of time.